Re: [PATCH v2 1/1] selinux: Transition to pasta_t in containers

[Stefano Brivio <sbrivio@redhat.com>]

On Fri, 16 May 2025 14:35:14 +0200
Paul Holzinger <pholzing@redhat.com> wrote:

> On 16/05/2025 14:22, Max Chernoff wrote:
> > Hi Paul,
> >
> > On Fri, 2025-05-16 at 13:59 +0200, Paul Holzinger wrote:
> >  
> >> So I did test this patch with podman's system and e2e test on podman
> >> v5.5.0 on fedora rawhide and I noticed one problem that caused some
> >> failures:
> >>
> >> podman build is broken with this policy. And I assume that means buildah
> >> would not work as well. The difference is that in the build case we do
> >> not pass a bind mounted namespace path under /run but rather
> >> /proc/$pid/ns/net as path to pasta. We get this error:
> >>
> >> pasta failed with exit code 1:
> >> Couldn't open network namespace /proc/360143/ns/net: Permission denied
> >>
> >> Logged avc:
> >> denied  { search } for  pid=360144 comm="pasta.avx2" name="360143"
> >> dev="proc" ino=2030208
> >> scontext=unconfined_u:unconfined_r:pasta_t:s0-s0:c0.c1023
> >> tcontext=unconfined_u:unconfined_r:container_runtime_t:s0-s0:c0.c1023
> >> tclass=dir permissive=0  
> > Odd, it works for me:
> >
> >      $ id -Z
> >      user_u:user_r:user_t:s0-s0:c0.c1023
> >
> >      $ podman --version
> >      podman version 5.4.2
> >
> >      $ pasta --version
> >      pasta 0^20250512.g8ec1341-1.fc42.x86_64
> >      Copyright Red Hat
> >      GNU General Public License, version 2 or later
> >        <https://www.gnu.org/licenses/old-licenses/gpl-2.0.html>
> >      This is free software: you are free to change and redistribute it.
> >      There is NO WARRANTY, to the extent permitted by law.
> >
> >      $ cat Containerfile
> >      FROM registry.fedoraproject.org/fedora-minimal:42
> >      RUN dnf install --assumeyes python3
> >
> >      $ podman build --no-cache --network=pasta .
> >      STEP 1/2: FROM registry.fedoraproject.org/fedora-minimal:42
> >      STEP 2/2: RUN dnf install --assumeyes python3
> >      Updating and loading repositories:
> >       Fedora 42 - x86_64 - Updates           100% |   8.3 MiB/s |   6.8 MiB |  00m01s
> >       Fedora 42 openh264 (From Cisco) - x86_ 100% |   7.7 KiB/s |   6.0 KiB |  00m01s
> >       Fedora 42 - x86_64                     100% |  12.3 MiB/s |  35.4 MiB |  00m03s
> >      Repositories loaded.
> >      Package                     Arch   Version        Repository      Size
> >      Installing:
> >       python3                    x86_64 3.13.3-2.fc42  updates     28.7 KiB
> >      Installing dependencies:
> >       expat                      x86_64 2.7.1-1.fc42   fedora     290.2 KiB
> >       libb2                      x86_64 0.98.1-13.fc42 fedora      46.1 KiB
> >       libgomp                    x86_64 15.1.1-1.fc42  updates    538.5 KiB
> >       mpdecimal                  x86_64 4.0.1-1.fc42   updates    217.2 KiB
> >       python-pip-wheel           noarch 24.3.1-2.fc42  fedora       1.2 MiB
> >       python3-libs               x86_64 3.13.3-2.fc42  updates     39.9 MiB
> >       readline                   x86_64 8.2-13.fc42    fedora     485.0 KiB
> >       tzdata                     noarch 2025b-1.fc42   fedora       1.6 MiB
> >      Installing weak dependencies:
> >       python-unversioned-command noarch 3.13.3-2.fc42  updates     23.0   B
> >
> >      Transaction Summary:
> >       Installing:        10 packages
> >
> >      Total size of inbound packages is 12 MiB. Need to download 12 MiB.
> >      After this operation, 44 MiB extra will be used (install 44 MiB, remove 0 B).
> >      [ 1/10] python3-0:3.13.3-2.fc42.x86_64  100% | 109.6 KiB/s |  29.7 KiB |  00m00s
> >      [...]
> >      [12/12] Installing python-unversioned-c 100% |   9.6 KiB/s | 424.0   B |  00m00s
> >      Complete!
> >      COMMIT  
> >      --> edfb5d3fee4c  
> >      edfb5d3fee4c729c0ec373150bd382e5a8461bc6ce18b14bcc12606d65ee185f
> >
> >      $ ps auxZ | grep pasta  # In another terminal while the above is running
> >      user_u:user_r:container_runtime_t:s0-s0:c0.c1023 test-us+ 497555 0.4  0.1 2533448 48028 pts/2 Sl+ 06:11   0:00 podman build --no-cache --network=pasta .
> >      user_u:user_r:pasta_t:s0-s0:c0.c1023 test-us+ 497680 1.1  0.0 206444 17188 ?     Ss   06:11   0:00 /usr/sbin/pasta --config-net --dns-forward 169.254.1.1 -t none -u none -T none -U none --no-map-gw --quiet --netns /proc/497672/ns/net --map-guest-addr 169.254.1.2
> >
> > What are the SELinux contexts of the network namespaces? This is what I
> > get:
> >
> >      $ ls -laZ $XDG_RUNTIME_DIR/netns $XDG_RUNTIME_DIR/containers/networks/rootless-netns /proc/self/ns/net
> >      ls: cannot access '/run/user/959/netns': No such file or directory
> >      lrwxrwxrwx. 1 test-user test-user user_u:user_r:user_t:s0-s0:c0.c1023    0 May 16 06:15 /proc/self/ns/net -> 'net:[4026531840]'  
> 
> It seems to be unconfined for me
> 
> lrwxrwxrwx. 1 test test 
> unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023  0 May 16 08:32 
> /proc/self/ns/net -> 'net:[4026531840]'
> 
> >
> >      /run/user/959/containers/networks/rootless-netns:
> >      total 0
> >      drwx------. 2 test-user test-user user_u:object_r:ifconfig_var_run_t:s0 40 May 16 06:05 ./
> >      drwx------. 3 test-user test-user user_u:object_r:user_tmp_t:s0         60 May 16 06:05 ../  
> /run/user/1001/containers/networks/rootless-netns:
> total 0
> drwx------. 2 test test unconfined_u:object_r:ifconfig_var_run_t:s0 40 
> May 16 06:26 .
> drwx------. 4 test test unconfined_u:object_r:user_tmp_t:s0 120 May 16 
> 06:26 ..
> 
> /run/user/1001/netns:
> total 0
> drwxr-xr-x. 2 test test unconfined_u:object_r:ifconfig_var_run_t:s0 40 
> May 16 07:31 .
> drwx------. 9 test test unconfined_u:object_r:user_tmp_t:s0 200 May 16 
> 06:19 ..

I'm getting the same issue with 'podman build' and the Containerfile
shared by Max. Running with SELinux in permissive mode, I'm getting:

# cat /var/log/audit/audit.log
type=AVC msg=audit(1747410763.621:130615): avc:  denied  { search } for  pid=1352409 comm="pasta.avx2" name="1352408" dev="proc" ino=7022238 scontext=unconfined_u:unconfined_r:pasta_t:s0-s0:c0.c1023 tcontext=unconfined_u:unconfined_r:container_runtime_t:s0-s0:c0.c1023 tclass=dir permissive=1
type=AVC msg=audit(1747410763.621:130616): avc:  denied  { read } for  pid=1352409 comm="pasta.avx2" name="net" dev="proc" ino=7022285 scontext=unconfined_u:unconfined_r:pasta_t:s0-s0:c0.c1023 tcontext=unconfined_u:unconfined_r:container_runtime_t:s0-s0:c0.c1023 tclass=lnk_file permissive=1
type=AVC msg=audit(1747410763.622:130617): avc:  denied  { read } for  pid=1352409 comm="pasta.avx2" scontext=unconfined_u:unconfined_r:pasta_t:s0-s0:c0.c1023 tcontext=unconfined_u:unconfined_r:container_runtime_t:s0-s0:c0.c1023 tclass=file permissive=1
type=AVC msg=audit(1747410763.622:130618): avc:  denied  { read } for  pid=1352409 comm="pasta.avx2" name="ns" dev="proc" ino=7022284 scontext=unconfined_u:unconfined_r:pasta_t:s0-s0:c0.c1023 tcontext=unconfined_u:unconfined_r:container_runtime_t:s0-s0:c0.c1023 tclass=dir permissive=1
type=AVC msg=audit(1747410763.622:130619): avc:  denied  { open } for  pid=1352409 comm="pasta.avx2" path="/proc/1352408/ns" dev="proc" ino=7022284 scontext=unconfined_u:unconfined_r:pasta_t:s0-s0:c0.c1023 tcontext=unconfined_u:unconfined_r:container_runtime_t:s0-s0:c0.c1023 tclass=dir permissive=1
type=AVC msg=audit(1747410764.622:130620): avc:  denied  { read } for  pid=1352417 comm="pasta.avx2" name="net" dev="proc" ino=7022285 scontext=unconfined_u:unconfined_r:pasta_t:s0-s0:c0.c1023 tcontext=system_u:system_r:container_t:s0:c609,c838 tclass=lnk_file permissive=1

and:

# audit2allow  -a


#============= pasta_t ==============
allow pasta_t container_runtime_t:dir { open read search };
allow pasta_t container_runtime_t:file read;
allow pasta_t container_runtime_t:lnk_file read;
allow pasta_t container_t:lnk_file read;

If I add those rules, everything works (well, I'm not saying that's
the solution...). This is a Fedora virtual machine with:

# uname -a
Linux passt.top 6.11.0-0.rc3.30.fc41.x86_64 #1 SMP PREEMPT_DYNAMIC Mon Aug 12 14:18:21 UTC 2024 x86_64 GNU/Linux
# rpm -qe podman passt
podman-5.5.0~rc2-1.fc43.x86_64
passt-0^20250512.g8ec1341-1.fc43.x86_64

To me those denials look reasonable, in the sense that I would expect
the namespace links to have container_runtime_t type.

By the way:

$ ls -laZ $XDG_RUNTIME_DIR/netns $XDG_RUNTIME_DIR/containers/networks/rootless-netns /proc/self/ns/net
lrwxrwxrwx. 1 sbrivio sbrivio unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023  0 May 16 15:59 /proc/self/ns/net -> 'net:[4026531840]'

/run/user/1001/containers/networks/rootless-netns:
total 0
drwx------. 2 sbrivio sbrivio unconfined_u:object_r:ifconfig_var_run_t:s0  40 May 15 15:00 .
drwx------. 4 sbrivio sbrivio unconfined_u:object_r:user_tmp_t:s0         120 May 15 15:00 ..

/run/user/1001/netns:
total 0
drwxr-xr-x. 2 sbrivio sbrivio unconfined_u:object_r:ifconfig_var_run_t:s0  40 May 15 15:00 .
drwx------. 8 sbrivio sbrivio unconfined_u:object_r:user_tmp_t:s0         220 May  6 08:02 ..

Max, could it be that you're running stuff with some customised SELinux
policy? By the way, with "unconfined disabled":

  https://bugzilla.redhat.com/show_bug.cgi?id=2330512

we seem to have unconfined_t as type for those links:

type=AVC msg=audit(1733378482.320:31258): avc:  denied  { open } for  pid=651955 comm="pasta.avx2" path="/proc/651954/ns" dev="proc" ino=2904841 scontext=staff_u:unconfined_r:pasta_t:s0-s0:c0.c1023 tcontext=staff_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 tclass=dir permissive=1

...but I'm not sure at which point in time exactly.

> >> I am not familiar with the selinux stuff but if this is a boolean that
> >> users can configure should this be documented in the man page here?  
> > I guess more documentation is always a good thing, but most of the other
> > container-related SELinux booleans seem to be undocumented:
> >
> >      $ sudo semanage boolean --list | grep ^container_
> >      container_connect_any          (off  ,  off)  Determine whether container can connect to all TCP ports.
> >      container_manage_cgroup        (on   ,   on)  Allow sandbox containers to manage cgroup (systemd)
> >      container_read_certs           (off  ,  off)  Allow all container domains to read cert files and directories
> >      container_use_cephfs           (off  ,  off)  Determine whether container can use ceph file system
> >      container_use_devices          (off  ,  off)  Allow containers to use any device volume mounted into container
> >      container_use_dri_devices      (on   ,   on)  Allow containers to use any dri device volume mounted into container
> >      container_use_ecryptfs         (off  ,  off)  Determine whether container can use ecrypt file system
> >      container_use_xserver_devices  (off  ,  off)  Allow containers to use any xserver device volume mounted into container, mostly used for GPU acceleration
> >      container_user_exec_content    (on   ,   on)  Allow container to user exec content
> >
> >      $ man -wK container_connect_any
> >      No manual entry for container_connect_any
> >
> >      $ man -wK container_manage_cgroup
> >      /usr/share/man/man1/podman-create.1.gz
> >      /usr/share/man/man1/podman-run.1.gz
> >      /usr/share/man/man7/podman-troubleshooting.7.gz
> >
> >      $ man -wK container_read_certs
> >      No manual entry for container_read_certs
> >
> >      $ man -wK container_use_cephfs
> >      No manual entry for container_use_cephfs
> >
> >      $ man -wK container_use_devices
> >      /usr/share/man/man1/sesearch.1.gz
> >      /usr/share/man/man1/podman-pod-clone.1.gz
> >      /usr/share/man/man1/podman-pod-create.1.gz
> >      /usr/share/man/man1/podman-build.1.gz
> >      /usr/share/man/man1/podman-farm-build.1.gz
> >      /usr/share/man/man1/podman-create.1.gz
> >      /usr/share/man/man1/podman-run.1.gz
> >      /usr/share/man/man8/setsebool.8.gz
> >
> >      $ man -wK container_user_exec_content
> >      No manual entry for container_user_exec_content
> >
> > I'll send a patch for the man pages tomorrow.

Wait a moment. I don't think something SELinux-specific belongs to
pasta's man page, because that's not relevant for all users and
distributions.

We could maintain that as an addition for Fedora and perhaps Gentoo,
but I wonder if it's really worth the effort. Besides, I think that:

# semanage boolean --list | grep pasta
pasta_allow_bind_any_port      (on   ,   on)  Allow pasta to allow bind any port

...this is the common practice to document those knobs (and where I
usually look for things). We wouldn't have much to add to this anyway.

-- 
Stefano